The purpose of the NIAID Clinical Pharmacology Quality Assurance (CPQA) program is to provide a comprehensive quality assessment program for clinical pharmacologic laboratories testing samples from subjects enrolled in NIAID-supported clinical studies. The CPQA program ensures the validity and inter- and intra-laboratory comparability of pharmacological study data by providing laboratories with materials for pharmacology proficiency testing and assay controls, and monitoring proficiency and assay data from each laboratory. The program also implements standards of performance for new pharmacology assays, develops and tests methods relating to the assays, and acquires, tests, stores and dispenses quality control materials and reagents. Thus, the CPQA program is critical to the scientific integrity of on-going and future studies concerning assessment of anti-HIV treatments and preventive measures.